1. Field of the Invention
The present invention relates to a flat membrane disk, particularly to a flat membrane disk for a rotary flat membrane separation apparatus which performs filtration intermittently.
2. Description of Related Art
A rotary flat membrane separation apparatus comprises a hollow rotary shaft and many flat membrane disks mounted on the shaft. The rotary flat membrane separation apparatus performs filtration by rotating the flat membrane disks while drawing water to be processed into them. In each of the flat membrane disks, a flat membrane is stretched at each of sides of a disk-shaped support body, which is so-called a disk, and the flat membranes and the disk are bonded to each other all around the outer periphery. The flat membrane disks are always rotated with the rotary shaft, whereby providing the flat membrane surfaces a flux so as to prevent the membrane surfaces from being clogged. Thus, the rotary flat membrane separation apparatus can perform filtration with a low power, which differs from other apparatuses that provides a flux to the membrane surface by circulating the water to be processed.
An intermittent suction method in which the water to be processed is drawn and filtrated intermittently is applied to the rotary flat membrane separation apparatus, so that the filtration capacity of the flat membrane can be maintained. By this method, the suction of the water to be processed is temporarily stopped so as to lower the adhesion of the contamination onto the membrane surface while the flat membrane disks are continuously rotated so as to separate and eliminate the contamination layer from the membrane surface. Moreover, some of the filtrated water within the flat membrane disks is reversed through the flat membrane by the centrifugal force, so that reverse cleaning effect can be achieved.
However, the conventional rotary flat membrane separation apparatus had a problem in that the flat membrane is separated from the support body and swollen when the filtrated water is reversed. Because of the fact that the flat membrane is swollen over and over at every time the suction filtration is stopped, the flat membrane is stretched unduly and wrinkled, and consequently the flat membrane is broken.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of the flat membrane disk that can prevent the flat membrane from swelling.
In order to achieve the above-described object, the present invention is directed to a flat membrane disk for a rotary flat membrane separation apparatus, the disk comprising: a circular support body connected to a rotary shaft; and a circular flat membrane stretched at a side of the support body by bonding the membrane to the support body at an outer periphery of the membrane, the membrane being partially bonded to the support body with a bonding part.
According to the present invention, since the membrane is bonded to the support body by the additional bonding part in the area of the membrane nearer to the outer periphery of the membrane than the rotary shaft, the membrane is prevented from being separated and swollen. Therefore, wrinkles on the membrane are prevented and the breakage of the membrane can thus be prevented.
In the present invention, the additional bonding part is in a form of a line or a dot so that the area of the additional bonding part is small; thus, the filtration capability of the membrane is not deteriorated.
Moreover, in the present invention, the additional bonding part is arranged in an area where the fluid that has passed through the membrane to the inside of the flat membrane disk flows in a reverse direction through the membrane to the outside of the flat membrane disk; so that the swelling of the membrane can be effectively prevented.